Protozoal parasitic infections of food species including mammals and birds are characterized by varying degrees of enteritis that results in decreased production and performance. In extreme cases, increased mortality is seen. However, even in less severe infections, losses in feed conversion efficiency and decreased weight gains may represent the difference between profit and loss in modern, intensive animal production situations. For example, coccidial infections are known to be a predisposing factor to other syndromes, in particular necrotic enteritis (a bacterial infection of the intestinal lining resulting in necrosis of the intestinal lining in various regions of the gut). Other protozoans, such as Histomonas and Cochlosoma, also lead to necrotic enteritis and increased mortality in severe cases, or in less severe cases poor feed utilization, stunted growth, and overall poor performance. The economic effects on producers can be catastrophic. It is standard poultry industry practice to reuse litter. However, such reused litter may serve as a protozoal reservoir for future infections.
Conventional disinfectants are relatively ineffective against protozoans. Thus, thorough cleaning of housing and strict biosecurity measures are necessary to maintain proper hygiene standards and reduce animal exposure. Unfortunately, due to relatively rapid turnaround of hosts (for example, the rapid replacement of flocks in broiler operations), a permanent reservoir of protozoal organisms is often maintained. Even a few organisms are capable of massive multiplication in a few weeks time. Accordingly, control measures beyond maintenance of proper hygiene are required.
Currently known methods of protozoal control include use of anti-protozoal medication. Anti-protozoal drugs are generally effective for their intended purpose, and advantageously may be provided in the feed or via the drinking water to animals being treated. However, a significant disadvantage of current drugs used for treatment/control of protozoa is that, over time, treated organisms may become resistant to particular drugs. Accordingly, different drugs must be used, often in rotation or in a staggered schedule (shuttle programs), to prevent development of resistant organisms. Even in cases where shuttle programs are implemented, it is possible that efficacy against protozoal infections will be compromised during the period when drugs are altered. Additionally, certain drugs, while useful in the control of protozoa, require a predetermined withdrawal period prior to slaughter to allow sale of meat, milk, eggs, etc. from treated animals.
There thus remains a need in the art for alternative methods for controlling protozoal infections in animals and birds. There is further a need in the art for alternative methods for controlling protozoa which do not risk creating resistant organisms.